Synthesis, crystal structure, spectroscopic and third-order nonlinear optical property studies on some dithiocarbazate complexes

Three SN Schiff base ligands derived from dithiocarbazate were prepared. Th eir neutral bis-ligand chelates, ML21 similar to 3[M = Ni (II), Cu (II), Pd (II) and Pt (II)], forming D-M-D and A-M-A type complexes were also prepar ed and characterized (D = donor, M = metal A = acceptor). Magnetic and spec troscopic data suggest a square-planar structure for the complexes. ESR spe ctra and variable-temperature magnetic susceptibility data supported a squa re-planar structure of Cu (II) chelate too. Single crystal X-ray diffractio n analysis of the copper( II) chelate established that the Schiff base liga nd lost a proton from its tautomeric thiol form and coordinated to metal vi a the mercapto sulfur and beta-nitrogen. The geometry around Cu (II) is squ are-planar with two equivalent Cu-N and Cu-S bonds, forming an electronic d elocalization system. The third-order NLO properties of them were also stud ied. The results show that the electro-donation group is quite helpful for the complexes exhibit higher third-order response.